This research is broadly concerned with determining basic principles of how the nervous system develops and with defining the principal dimensions of neural ontogeny affected by different genotypes within the same species. Specifically, we are analyzing the embryonic spinal cords of different inbred strains of mice in order to define developmental similarities and differences in the formation of the neuronal connections which comprise the cutaneous reflex arc. We are employing reflex behavioral testing, tritiated thymidine radioautography, and a variety of neuroanatomical methods in this research. It is anticipated that these studies will contribute toward both an understanding of normal brain development and the neuroembryological processes regulated by genes. It is hoped that such knowledge will be useful for investigations of cases where genetically-associated abnormalities of brain development are the suspected basis of adult brain disorders. BIBLIOGRAPHIC REFERENCES: Vaughn, J.E., Menrikson, C.K. Chernow, C.R., Grieshaber, J.A., and Wimer, C.C. Genetically-associated variations in the development of reflex movements and synaptic junctions within an early reflex pathway of mouse spinal cord. J. Comp. Neurol., 161:541-554, 1975. Wood and McLaughlin, B.J. The visualization of cancanavalin-A binding sites in the intraperiod line of rat sciatic nerve myelin. J. Neurochem., 24:233-235,1975.